1. Field of the Invention
The present invention relates to an electrostatic chuck and a manufacturing method thereof.
2. Description of the Related Art
Heretofore, in a manufacturing apparatus of a semiconductor device and a manufacturing apparatus of a liquid crystal device, an electrostatic chuck has been used in order to hold a substrate during a manufacturing process, for example, a deposition process and an etching process, and in order to convey the substrate. In general, the electrostatic chuck has a structure in which a dielectric electrode for generating electrostatic force is embedded in a base made of ceramics. Moreover, there is also an electrostatic chuck in which a resistance heating body is further embedded in the ceramics. A material of the base of the electrostatic chuck as described above is, for example, alumina having excellent heat resistance and corrosion resistance and high volume resistivity.
In recent years, for the electrostatic chuck, higher corrosion resistance than heretofore has been being required. For example, corrosion resistance sufficient for in-situ cleaning in the etching process of the semiconductor device is required. The in-situ cleaning is not a method, like conventional wet etching, of etching a semiconductor wafer after taking out the semiconductor wafer to the outside from a chamber where heating treatment and deposition treatment are performed therefore, but is a method of etching the semiconductor wafer by a plasma environment of halogen-series corrosive gas in the chamber. The electrostatic chuck will be exposed to such a severe plasma environment of the halogen-series corrosive gas.
In order to enhance corrosion resistance of a ceramic member applicable to the electrostatic chuck, a ceramic member has been proposed, in which an yttria sintered body having higher corrosion resistance than alumina is bonded to an upper surface of an alumina sintered body (Japanese Patent Laid-Open Publication No. 2006-128603).
The ceramic member described in Japanese Patent Laid Open Publication No. 2006-128603 contains a large amount of carbon in the alumina sintered body in order to enhance mechanical strength of the alumina sintered body. With regard to the ceramic member including such an alumina sintered body containing the large amount of carbon, the high mechanical strength thereof becomes advantageous, for example, when the ceramic member is applied to a heater. However, since carbon has conductivity, when the ceramic member is applied to the electrostatic chuck, there has been a case where the volume resistivity of alumina is decreased by a high temperature in an environment where the electrostatic chuck is used. In this case, there has been an apprehension that a current supplied to a dielectric electrode may be transmitted to alumina on the periphery of the dielectric electrode and flown to other portions, that is, that a so called leak current may be increased. There has been an apprehension that the increase of the leak current may cause a malfunction particularly in the case of an electrostatic chuck in which the dielectric electrode is disposed in a bonded portion between the alumina sintered body and the yttria sintered body. This is because there is a possibility that the leak current may be transmitted along the bonded portion to a surface of the base.
Moreover, in the ceramic member described above in Japanese Patent Laid-Open Publication No. 2006-128603, the yttria sintered body having high corrosion resistance will be formed only on an upper surface of the base when the ceramic member is applied to the electrostatic chuck. Here, with regard to the electrostatic chuck, not only an upper surface thereof but also a side surface thereof is exposed to the severe corrosive environment in the chamber where the electrostatic chuck is subjected to the treatment such as etching. Accordingly, in the electrostatic chuck in which the above-described yttria sintered body is formed only on the upper surface of the base, corrosion resistance of a side surface portion thereof is not always sufficient depending on etching conditions, and there has been a case where the insufficient corrosion resistance causes contaminations and particles.
The present invention advantageously solves the above-described problems. It is an object of the present invention to provide an electrostatic chuck, in which the leak current is suppressed, and the corrosion resistance is further excellent, and also to provide an advantageous manufacturing method of the electrostatic chuck.